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Discussion Starter #1
I put a Pioneer gm-d1004 4 x 45 RMS, 100 peak mini amplifier in my car using high level input for signal due to factory head unit, tapped into a 20AMP fuse for power. I was very pleased with the result. However the 6.5 factory speakers 20 watt distorted at high volumes so I decided to replace the front door speakers with Kenwood kfc-x174's 80 RMS, 240 peak. 100w input as specified in the pioneer manual.

Problem, whilst they do go louder before distorting there is still bass distortion from around 60% - 70% volume and I am trying to understand why given the amp supplies less power than the speakers can handle, there is no gain setting on this amp unfortunately, I presume if there was I would turn the gain down.

Do I need less powerful speakers, any pointers would be appreciated!?
 

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Could be a crappy signal from the OEM stereo (very common, and one main reason we go aftermarket). It could also be from a lack of high pass filter, does the amp have a HPF?
 

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Could be coming from the deck at upper levels. Have you try adjusting relative tone controls in the deck to see if that remedies the issue? Are you using the amp's supplied crossover?

Man & Machine... Power Extreme!
 

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Discussion Starter #4
The amp has hi/low switches for front rear channels which are both set to off, I do have the bass up slightly on the oem headunit, mid and treble are center.
 

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Turn the HPF on. It’s set for 80hz, which will reduce the bass, but those speakers have no business playing below 80hz anyway, and that’s the likely cause of your distortion problem.
 

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Discussion Starter #6
Yes, that has helped thanks and they do go louder, I never thought about doing that as they are full range supposedly.

Something odd happened though, I also have a small kenwood underseat sub with high level speaker input, when I did this the sub lost its basseven though it gets its input before the pioneer amp pioneer amp, however when I reversed the phase from 0 to 180 on its controller the bass came back. I reverted to the original setup hp off to double check and yes had to set sub back to phase 0.

Why would that be?
 

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There’s really no such thing as a fullrange speaker. If there way we could use one for the left, and one for the right to eliminate a bunch of problems that come with having multiple speakers.

So, after you set the HPF the sub shut off completely? And either switching the phase, or turning the HPF off brought it back?
 

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Discussion Starter #8
No it did not shut of completely but there was much less bass until phase switched on its controller or turning the subs volume up from 50% go 100%.
 

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Well, by setting the HPF your cut a ton of bass from the 6.5” speakers. That bass was being reinforced by the subwoofer, so without the bass from the 6.5’s it will reduce the bass. The sub is still playing the same as it always did.
 

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Discussion Starter #10
But if I turn the hpf off , I lose bass on the sub again until I put its phase back to the original setting,
 

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That’s why it has a phase switch. With the mids playing bass they need to be in phase with the sub, so you flip that switch and leave it wherever you get the best bass. With the HPF on the mids you’re cutting a lot of bass, but there is still some overlap, set the phase at whichever setting gives the best bass.
 

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Most likely the factory deck is clipping hard and the amplifier doesn’t know the difference so what goes in goes out it’s 45 watts more power. My Ford Sync factory deck starts clipping at about 55-60% volume.
 

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Discussion Starter #13
I installed a polarity checker on my android phone which is very cool, confirmed all the doors are in phase and selecting hpf on or off does not change this. Also confirmed that sub set to phase 180 does indeed put it out of phase with the doors which gives mores bass when hpf is on than when it is off for some reason.
 

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If you get more bass then you are closer to being in phase. Leave it wherever you get the most bass, that setting is closest to aligning the acoustic phase. Electrical phase (polarity) is irrelevant.
 

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Discussion Starter #15
I feel now the sound is washed out lacking substance, is this just how it is with a 80Hz LPF? Do most people with an amp and sub do LPF on door speakers?


What options do I have to combat the original issue other than LPF if I was to purchase some new equipment (not head unit or too expensive) are there alternative 6.5 speakers?


I have the kenwoods in my front doors, I am thinking eventually I might move them to the rear doors and buy a reasonably priced component set that would go well with my existing amp, that will replace the front door 6.5’s and the dash 3.5,s which are daisy chained on the same channel to the front doors, preferably something with an inline crossover so I can hook the small speaker/tweeter to the existing wiring in the dash. Does anything come to mind that fits this?
 

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Discussion Starter #18
Not sure to be honest, If it does I don't think it is significant. Its a GM (Opel/Vauxhall) Navi 900.

I have been playing around again at lunch time, I think I basically need to turn the sub (Kenwood KFC-PSW8) to a higher/max volume which definitely helps or get another sub. In the past I turned it down as too bassy, but I guess with the hpf on the doors it needs to work a lot harder.
 

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Discussion Starter #19
With my amp and powered sub all being connected via high level input due to the factory head unit, and given the fact the hpf 80hz slope is set on the amp which powers the door and dash speakers, would it be advisable to to turn the bass up to full on the head units "3" band equaliser to maximise the bass signal going to the sub? This does seem to have a significant effect on the bass of the sub depending where it is set. The sub has a lpf that goes 50 to 125 hz, I have this set some where between 70 - 80.
 

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You can, but increasing the bass with the tone controls will cause the head unit to start clipping the signal at a lower volume level which will introduce distortion. Increasing it all the way will usually clip the signal really fast.
You don't necessarily need to low pass the sub at the exact frequency the high pass of the other amp kicks in. Use the low pass that you feel sounds best since you can adjust that crossover.
 
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